508 MILK 



absorbent cotton and the milk drawn off with a pipet, or a fine-pointed tube 

 attached to a Chapman air pump. Only about 2 mm. of milk are left above 

 the sediment which is in the bottom of the sedimentation tube. 



The stain, which is an aqueous solution of safranin 0, soluble in water, 

 is then added very slowly from an opsonizing pipet. The important thing is 

 to mix stain and milk so slowly that clotting does not take place. The stain 

 is added until a deep opaque rose color is obtained. After standing three 

 minutes, by means of the opsonizing pipet, which has been washed out in 

 hot water, the stained sediment is then transferred to slides. A small drop 

 is placed at the end of each of several slides and spread by means of a glass 

 spreader, as in Wright's method for opsonic index determinations. 



In an unheated milk the polymbrphonuclear leukocytes have their pro- 

 toplasm slightly tinged or are unstained. 



In heated milk the polymorphonuclear leukocytes have their nuclei 

 stained. In milk heated to 63 C. or above, practically all of the leukocytes 

 have their nuclei definitely stained. When milk is heated at a lower tem- 

 perature the nuclei are not all stained above 60 C. The majority, however, 

 are stained. 



87. Specific Gravity. The specific gravity of certified milk shall range 

 from 1.029 to 1.034. 



88. The specific gravity shall be determined at least each month. 



The Quevenne lactodensimeter is recommended for the determination 

 of the specific gravity. It is made like an ordinary aerometer and divided 

 into degrees which correspond to a specific gravity from 1.014 to 1.040, or 

 only 1.022 to 1.038, since by the latter division a greater space is gained 

 between the different degrees without unduly lengthening the instrument. 

 From such a lactodensimeter one can easily read off four decimal places. 



The milk the specific gravity of which is to be determined is well shaken 

 and poured into a high glass cylinder of suitable diameter; the aerometer is 

 dropped in slowly, in order to prevent its bobbing up and down. (The bulb 

 should be free from adhering air bubbles.) The figures on the stem are the 

 second and third decimals of the numbers of the specific gravity, so that 34 

 is to be read 1.034. For this examination, the temperature of the milk must 

 be 15 C. (60 F.) ; if it is not, the specific gravity of the milk at 15 C. must 

 be calculated from the specific gravity found and from the temperature, for 

 in milk inspection and analysis this is the standard. 



METHODS AND REGULATIONS FOR THE MEDICAL EXAMINATION OF EMPLOYEES, 

 THEIR HEALTH AND PERSONAL HYGIENE 



89. A medical officer, known as the attending dairy physician, shall be 

 selected by the commission, who should reside near the dairy producing 

 certified milk. He shall be a physician in good standing and authorized by 

 law to practice medicine; he shall be responsible to the commission and sub- 

 ject to its direction. In case more than one dairy is under the control of the 

 commission and they are in different localities, a separate physician should 

 be designated for employment for the supervision of each dairy. 



90. Before any person shall come on the premises to live and remain as 

 an employee, such person, before being engaged in milking or the handling of 

 milk, shall be subjected to a complete physical examination by the attending 

 physician. No person shall be employed who has not been vaccinated re- 

 cently or who upon examination is found to have a sore throat, or to be suf- 

 fering from any form of tuberculosis, venereal disease, conjunctivitis, diar- 

 rhea, dysentery, or who has recently had typhoid fever or is proved to be a 

 typhoid carrier, or who has any inflammatory disease of the respiratory tract, 

 or any suppurative process or infectious skin eruption, or any disease of an 

 infectious or contagious nature, or who has recently been associated with chil- 

 dren sick with contagious disease. 



91. In addition to ordinary habits of personal cleanliness all milkers shall 

 have well-trimmed hair, wear close-fitting caps, and have clean-shaven faces. 



